Warping and Residual Stress Analysis using the Abaqus Interface for Moldflow

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Residual stresses may be introduced into plastic parts produced by the injection molding process. As a result, the part may warp or experience a reduction in strength. The design of an injection molded product can be improved if the effect of residual stresses on the final shape and performance of the product are predicted accurately. Abaqus and Moldflow can be used for this purpose. The residual stresses generated by the solidifi-cation of the plastic material are computed by Moldflow and transferred to Abaqus using the Abaqus Interface for Moldflow. The component can then be structurally analyzed with Abaqus to determine warpage and/or response to in-service loading. In this Technology Brief, this methodology is demonstrated with two case studies.

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Warping and Residual Stress Analysis using the Abaqus Interface for Moldflow

  1. 1. Abaqus Technology Brief TB-07-MOLD-1 Revised: August 2007 .Warping and Residual Stress Analysis using the Abaqus Interfacefor MoldflowSummaryResidual stresses may be introduced into plastic partsproduced by the injection molding process. As a result,the part may warp or experience a reduction in strength.The design of an injection molded product can beimproved if the effect of residual stresses on the finalshape and performance of the product are predictedaccurately. Abaqus and Moldflow can be used for thispurpose. The residual stresses generated by the solidifi-cation of the plastic material are computed by Moldflowand transferred to Abaqus using the Abaqus Interface forMoldflow. The component can then be structurallyanalyzed with Abaqus to determine warpage and/orresponse to in-service loading. In this Technology Brief,this methodology is demonstrated with two case studies.Background Key Abaqus Features and BenefitsThe quality of a product manufactured by the injectionmolding process can be sensitive to residual stress. Mechanical property, finite element mesh, andExcessive residual stress can lead to warping, shrinkage, residual stress data can be easily transferredor unexpected failures when the part enters service. from Moldflow to AbaqusFurther, product assembly may be hindered or preventedif warping exceeds a given tolerance. In order to improve The inclusion of residual processing stresses inthe designs of injection molded products, it is important to an Abaqus analysis allows for more accurateunderstand the magnitude, distribution, and effects of simulation of the injection molded productprocess induced residual stresses.Moldflow is mold design software that can be used toestimate the residual stresses in a molded product. Analysis ApproachIn order to determine how these residual stresses affectthe final shape and performance of the product, a The procedure for performing a warping and stressdetailed structural analysis that accounts for the residual analysis on a molded product begins with a simulation ofstresses is necessary. Abaqus can be used for this the injection molding process using Moldflow.purpose, and the Abaqus Interface for Moldflow provides The Moldflow analysis results include descriptions of thefor the transfer of stress results from a Moldflow analysis material properties and the distribution of residual stressto an Abaqus analysis. in the solidified part. The Abaqus Interface for Moldflow is then used to translate this data into a form that can be used by Abaqus; specifically, the interface generatesIn this Technology Brief we present two case studies in files that contain mesh information, residual stressthe structural analysis of molded products. The first case results, and material properties of the plastic. These datastudy presents a plastic chair model and the second case are then used in subsequent Abaqus analyses forstudy involves the analysis of a cellular phone cover. modeling warping and the effects of residual stresses.
  2. 2. 2The discretized models of the molded chair and cellular Contour plots of Mises stress from the Abaqus/Standardphone cover are shown in Figure 1. For both models, the warping analyses are shown for the chair and phoneMoldflow analyses used shell elements with 21 layers cover models in Figures 4 and 5. It can be clearly seenthrough the thickness. The warping simulations were that, with the warping deflection comes a reduction in theperformed using the static analysis capability in magnitude of Mises stress stored in both parts.Abaqus/Standard. Figure 3: Warping displacements [m] for the phone cover Figure 1: Chair and phone cover meshes. model.Results and DiscussionThe deformed shapes of the chair and cell phone covermodels after the warping analyses in Abaqus/Standardare shown in Figures 2 and 3. Figure 4: Mises stress [Pa] for the chair model: BeforeFigure 2: Warping displacements [m] for the chair model. warping (Left) and after warping (Right).
  3. 3. 3 Conclusion Abaqus provides a powerful capability for performing detailed structural analyses. Moldflow provides the ability to calculate residual stresses and material properties for an injection molded product. By providing the means for transferring Moldflow results into an Abaqus analysis, the Abaqus Interface for Moldflow allows for a more accurate and efficient design process. Figure 5: Mises stress [Pa] for the phone cover model: Before warping (Left) and after warping (Right).Abaqus ReferencesFor additional information on the Abaqus capabilities referred to in this brief, please see the followingAbaqus 6.11 documentation reference: Abaqus Interface for Moldflow Users Manual.About SIMULIASIMULIA is the Dassault Systèmes brand that delivers a scalable portfolio of Realistic Simulation solutions including the Abaqus prod-uct suite for Unified Finite Element Analysis, multiphysics solutions for insight into challenging engineering problems, and lifecyclemanagement solutions for managing simulation data, processes, and intellectual property. By building on established technology, re-spected quality, and superior customer service, SIMULIA makes realistic simulation an integral business practice that improves prod-uct performance, reduces physical prototypes, and drives innovation. Headquartered in Providence, RI, USA, with R&D centers inProvidence and in Suresnes, France, SIMULIA provides sales, services, and support through a global network of over 30 regionaloffices and distributors. For more information, visit www.simulia.comThe 3DS logo, SIMULIA, Abaqus and the Abaqus logo are trademarks or registered trademarks of Dassault Systèmes or its subsidiaries, which include ABAQUS, Inc. Other company, product andservice names may be trademarks or service marks of others.Copyright © 2007 Dassault Systèmes

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